ML350 G5 mix and match options

So, we were recently 'gifted' some ML350 servers from an offsite location. I currently have all Dell gear in my shop and have no hands-on with HPE gear so, here I am looking to you. :)

I have 4 ML350 servers, 1 G4 and 3 G5. What I want to do is make one decent machine out of it..

I'm focusing on the 3 G5 boxes at this point as they are all identicle: 2GB RAM, Xeon 5130 (single proc), and 8 bay, 2.5" HDD cage.

I want to pull all the RAM into one box, double up on the CPU, and double up on hte HDD cage.

My questions: what do I need hardware/software wise in order to do this? I know I need a PMM to load up the 2nd processor but can I actually use a second HDD cage and 8 more drives natively? Can I pull the RAID expansion card from the G4 (HP SMART ARRAY 642 CONTROLLER (012591-000) in the G5 to accomodate the second cage?

A lot of questions, but I'm trying to work with what I have as money is non-existent. (At least according to the folks that make way more that me...)